1. Field of the Invention
The present invention relates generally to a folding score and a method and apparatus for forming such folding score. More particularly, the present invention relates to a folding score and a method and apparatus for forming such folding score in a panel of sheet material such as corrugated paperboard or the like.
2. Description of the Prior Art
The processing of sheet material to transform such sheet material to a useable form such as a box, display device or the like, normally involves utilizing a rotary die or flat die to cut a blank from the sheet material and provide it with various scores, slits, etc. for the purpose of forming tear strips, punch outs, fold lines, etc. in the blank. These cuts, scores, slits, etc. are commonly formed through the use of cutting and creasing rules mounted into or onto the die.
To facilitate folding of sheet material such as corrugated paperboard, fold lines are formed in the material by scoring dies commonly referred to as creasing rules. In the past, various configurations of folding lines or folding scores have existed including, among others, a single score in which the sheet material is compressed or creased along a single line, a double score in which the material is compressed or creased along a double, parallel line, a wavy score such as that reflected in U.S. Pat. No. 5,221,249 in which the material is compressed or creased along a wavy line, a broken score in which the material is compressed or creased along a single or double line with intermittent areas of non-compression, and a slit score in which portions of the material are cut along a single or double line, with areas where the material is not cut.
A problem which has existed and continues to exist with respect to corrugated paperboard folds, and particularly corrugated paperboard folds along a line substantially parallel to the corrugation flutes, is the tendency of the fold lines to "wander" and not fold consistently. Specifically, fold lines formed with existing score configurations or creasing rules are susceptible to shifting to one side or the other during the actual folding process, thereby resulting in "phantom" fold lines which are laterally spaced from the intended fold line or resulting in a fold which is not completely straight or square.
One effort to solve this problem is described in U.S. Pat. No. 5,194,064. This patent discloses a single, elongated primary score and a plurality of elongated creasing members that extend laterally outwardly from opposite sides of the primary score. This score, however, is significantly wider than conventional scores, thus resulting in a significant amount of the corrugated sheet material being compressed. This not only limits the use of this score mechanism to fold lines which are significantly spaced from one another, but also results in decreasing the strength of the sheet material along the fold line as a result of the excess crushing of the corrugation flutes.
Accordingly, there is a need in the art for a folding score for a sheet material such as corrugated paperboard or the like which provides for a consistent fold of the corrugated material along the fold line and precludes or minimizes the tendency of the fold line to wander or shift to one side or the other of the intended fold line. There is also a need in the art for an apparatus and method for forming such a folding score.